clarified signature: more arguments;

--- a/src/Pure/General/http.scala	Sun Oct 02 17:41:34 2022 +0200
+++ b/src/Pure/General/http.scala	Thu Oct 06 11:38:23 2022 +0200
@@ -276,10 +276,11 @@
   }
 
   def server(
+    port: Int = 0,
     name: String = UUID.random().toString,
     services: List[Service] = isabelle_services
   ): Server = {
-    val http_server = HttpServer.create(new InetSocketAddress(isabelle.Server.localhost, 0), 0)
+    val http_server = HttpServer.create(new InetSocketAddress(isabelle.Server.localhost, port), 0)
     http_server.setExecutor(null)
 
     val server = new Server(name, http_server)